May 3, 2012 (London, United Kingdom) — The lead researcher of a small study that has found that energy drinks can increase blood pressure and cause tachycardia and arrhythmias in healthy volunteers believes that sales of these products should be regulated [1].

Reporting her findings at the European Society of Hypertension (ESH) European Meeting on Hypertension 2012, nephrologist Dr Magdalena Szotowska (Medical University of Silesia, Katowice, Poland) also told heartwire that doctors "should advise people with hypertension, heart problems, and diabetes not to drink these. That would be my advice." Habitual consumers are the other group most at risk from the adverse effects of these products, she believes.

Szotowska thinks it is the combination of substances found in energy drinks--which are 10% sucrose and include among other things caffeine, taurine, and inositol--that are responsible for the effects, rather than the caffeine per se. As well as the adverse effects seen on the circulatory system, she found the drinks increased anxiety and insomnia among the participants in her study.

She noted that in Poland there have been many reports in the newspapers about car accidents and "road-rage" incidents in so-called "chain-drinkers" of these beverages, even when they are consumed without alcohol. Overconsumption is particularly dangerous, she says, adding that few people realize this is a problem; she believes it is time to raise awareness of this issue.

Energy Drink With 360 mg of Caffeine Linked to Increased Heart Rate, BP

Szotowska said there are many, many products in the multibillion-dollar worldwide energy drinks market, the best-known being Red Bull. In her study, she randomized, on a double-blind basis, 18 healthy volunteers, aged 20 to 35 years, to drink one of two strengths of energy drink, one containing 120 mg of caffeine and the second containing 360 mg of caffeine, or placebo. Measurements of BP and pulse rate were performed before and after ingestion.

The 120-mg caffeine drink is equivalent to one large can of Red Bull in Poland or a small can of Red Bull concentrated, she said. The 360-mg caffeine drink was chosen because this represents the largest amount of caffeine found in the biggest bottle of energy drink on sale there, she noted. However, she said that tablets are now available in supermarkets and convenience stores; these are cheap and can be made up with water to whatever strength consumers want.

Consumption of the energy drink containing 120 mg of caffeine didn’t significantly influence blood pressure and pulse rate compared with placebo. But the drink containing 360 mg of caffeine did lead to a significant increase in mean systolic (+9.0 mm Hg, p=0.033) and diastolic (+9.4 mm Hg, p=0.028) BP and an increase in mean heart rate (+5 bpm, p=0.042) compared with placebo. And all of those who drank the energy drink with 360 mg of caffeine developed cardiac arrhythmias with tachycardia, anxiety, and insomnia.

Szotowska said she is not convinced the systolic-BP surge was necessarily due to the drink, as this occurred only 15 minutes after consumption. But the diastolic peak, occurring 30 minutes afterward, and the tachycardia, 90 minutes after drinking, likely were linked, she noted.

Szotowska told heartwire she was surprised by the findings, having been a consumer of energy drinks herself prior to the research: "We didn't know that this will happen when we planned this study; we were shocked." The fact that it was the product with the larger amount of caffeine in it that caused most problems indicates that those who "chain-drink" these products are most at risk, she observes.

She is now planning another study in a larger number of people.

Other Reports of Toxicity With Energy Drinks; Further Research Needed

A quick search of PubMed reveals other research warning of the possible problems associated with energy drinks, which are popular with teenagers and young adults.

This year alone, scientists in the US found that one can of Red Bull containing 80 mg of caffeine increased BP compared to 80 mg of caffeine alone in healthy volunteers in a pilot study [2] and an Australian poisons control center has reported on almost 300 cases of toxicity due to ingestion of these drinks [3], with the mean number of drinks consumed in one session being five and the average age of those drinking them being 17. The most common symptoms reported included palpitations, agitation, tremor, and gastrointestinal upset. There were 21 subjects with signs of serious cardiac or neurological toxicity, and 128 subjects (including 57 who did not coingest anything else) were hospitalized.

US pediatricians are also calling for urgent, further research into the safety of these products, noting that regulation may be required in the future [4].

There have also been media reports pertaining to energy drinks, with reports that a 14-year-old girl died after drinking such products last year [5], and calls for energy drinks to be regulated in South Africa [6].

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